bolt calculation

The simplest answers are:

1. Neglecting any preload in the bolt and consequently any friction forces:

The shear stress is simply the force divided by the area

τ=F/A

Where τ = shear stress

F = Force applied in shear to the bolt

A = Area of the bolt (Note: it makes a difference either through the shank or the threaded section)

NOTE: The allowable shear stress in a bolt is usually taken as 62% of the tensile strength of the bolt.

2. This question is a little more complicated because bolted joints are usually preloaded and the 'extension' (tensile) force 'seen' by the bolts is not that intuitive - it depends on the stiffness of the joint. For example - if you hung 100 lbs from a preloaded single bolt joint - the bolt WILL NOT experience a 100 lbs force.

In any case - if you know for certain the tensile force, or if you neglect preload. The equation/criteria to ensure bolt integrity is to confirm the sum of the squares of the ratios of stresses are less than or equal to one, that is:

(Shear applied/Shear allowed)² + (Tensile applied/Tensile allowed)² ≤ 1

3. The NASA guide applies to all industries. If you require more information - just get back to me by replying to this post.

thanks a lot.

i want more info. if you can send it to my mail eyal@aob.co.il i will appreciate.

i calculate the combined force by von mises==> equal stress= (stress^2+3*shear^2)^0.5 but your way seems easier.

I sent you an email.

If for whatever reason you do not receive it, just reply here.

Regards.

You are right continue to use the equation of von Mises.

Do not neglect the shear stresses from tightening the bolt they are also active in stressing the material.

There is now a VDI/VDE code accepted world wide for calculaion of bolts. Is based on many research done in Germany especially generated by the requirements of the automotive industry.